Think Python - Denison University

158 Chapter 16. Classesand functions16.6 Glossaryprototype and patch: Adevelopmentplanthatinvolveswritingaroughdraftofaprogram,testing,and correcting errorsas they arefound.planned development: A development plan that involves high-level insight into the problem andmore planning than incremental development or prototype development.pure function: A function that does not modify any of the objects it receives as arguments. Mostpure functions arefruitful.modifier: A function that changes one or more of the objects it receives as arguments. Most modifiersare fruitless.functional programming style: A style of program design in which the majority of functions arepure.invariant: A condition that should always be trueduring theexecution of aprogram.16.7 ExercisesExercise16.6 Writeafunctioncalledmul_timethattakesaTimeobjectandanumberandreturnsanew Time object that contains theproduct ofthe original Time and the number.Then use mul_time to write a function that takes a Time object that represents the finishing timein a race, and a number that represents the distance, and returns a Time object that represents theaverage pace (timeper mile).Exercise 16.7 Write a class definition for a Date object that has attributes day, month and year.Writeafunctioncalledincrement_datethattakesaDateobject,dateandaninteger,n,andreturnsa new Date object that represents the day n days after date. Hint: “Thirty days hath September...”Challenge: does your function deal with leap years correctly? See wikipedia.org/wiki/Leap_year.Exercise 16.8 The datetime module provides date and time objects that are similar to the Dateand Time objects in this chapter, but they provide a rich set of methods and operators. Read thedocumentation atdocs.python.org/lib/datetime-date.html.1. Use the datetime module to write a program that gets the current date and prints the day ofthe week.2. Write a program that takes a birthday as input and prints the user’s age and the number ofdays, hours, minutes and seconds until their next birthday.